Add publishing of website to Github workflow

[nadvolod]

Currently we publish the website by running the following command:

GIT_USER=nadvolod CURRENT_BRANCH=master yarn run publish-gh-pages

It might be better and easier to do this automatically through a GH workflow after the Docs changes are merged into master

[titusfortner]

maybe this? https://github.com/clay/docusaurus-github-action